Street sweeper with a hydrostatic transmission

ABSTRACT

A self-propelled street sweeper having sweeping equipment including a rotatable broom and a conveyor means for depositing material dislodged by the broom into a hopper characterized by a single engine whose output is connected by a power splitting mechanism to a drive train connected to a pair of wheels of the sweeper for propelling the sweeper and to a drive means for actuating the sweeping means. The drive train includes a hydrostatic transmission which enables the operator to vary the speed and direction of movement of the sweeper independently of the speed of the rotating broom which is governed by the engine speed. The operator controls the transmission through a foot pedal which may be disposed on the right hand or the left hand side of the sweeper or a pair of pedals may be provided to provide a dual control system.

[ Dec. 17, 1974 STREET SWEEPER WITH A HYDROSTATIC TRANSMISSION Inventors: Donald L. Hildebrand, Union;

Ernest F. Prescott; Donald G. Kirk, both of Elgin, all of I11.

Primary Examiner-Edward L. Roberts Attorney, Agent, or Firm-Hill, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson [5 7 ABSTRACT A self-propelled street sweeper having sweeping equipment including a rotatable broom and a conveyor means for depositing material dislodged by the broom into a hopper characterized by a single engine whose output is connected by a power splitting mechanism to a drive train connected to a pair of wheels of the sweeper for propelling the sweeper and to a drive means for actuating the sweeping means. The drive train includes a hydrostatic transmission which enables the operator to vary the speed and direction of movement of the sweeper independently of the speed of the rotating broom which is governed by the engine speed. The operator controls the transmission through a foot pedal which may be disposed on the right hand or the left hand side of the sweeper or a pair of pedals may be provided to provide a dual control system.

19 Claims, 9 Drawing Figures PATENTEQ CZC I 7 I974 SHEET 10F 4 Fig. 3

PATENTEL BEE] 7 I974 SHEET 30F 4 PATENTED DEB! 71974 SHEETRDF4 STREET SWEEPER WITH A IIYDROSTATIC TRANSMISSION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to a self-propelled street sweeper utilizing a single engine for driving both the sweeping brooms and conveyors and for propelling the sweeper.

2. Prior Art Self-propelled street sweepers utilizing a single engine to both propel the street sweeper and to drive the sweeping attachment such as side brooms, main brooms, and conveyors are known in the art. In the sweepers, a problem exists. It is difficult to maintain the broom at a desired operating speed while propelling the sweeper at different speeds or in a reverse direction. Thus, in many conventional sweepers, flexibility in the use of the sweeper has been limited due to the use of a single propulsion unit or engine for providing the propulsion power and for driving the sweeping equipment.

SUMMARY OF THE INVENTION The present invention is directed to a self-propelled sweeper having sweeping means including a rotatable broom and conveying means for depositing material dislodged by the broom into a hopper which sweeper utilizes a single engine for driving the sweeping means and for propelling the sweeper through a drive train which includes a hydrostatic transmission having a hydrostatic motor in fluid communication with the variable displacement pump which transmission includes means for controlling the volume and direction of the displacement of the pump to control the speed and direction of movement of the sweeper and linkage means extending from an operator positioned on the sweeper and connected to the control means so that the speed and direction of the movement of the street sweeper can be controlled independently of the speed of the sweeping means.

Accordingly, it is the object of the present invention to provide a self-propelled sweeping device having the sweeping means operating at the desired speed while the speed and direction of the sweeper is independently controlled through various speeds over the street surface.

Another object of the present invention is a selfpropelled sweeper which is capable of having its movements stopped or reversed while the sweeping equipmentor means continues to operate at a preset speed.

Another object of the present invention is to provide a self-propelled sweeper device which is easy and economical to operate under various sweeping conditions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 3 is a plan view of the drive train and power take off of the present invention with portions removed for purposes of illustration;

FIG. 4 is a view taken along lines IV-IV of FIG. 3;

FIG. 5 is an enlarged view with portions in cross section of the control means for the hydrostatic transmission;

FIG. 6 is a partial view taken along lines VIVI of FIG. 5;

FIG. 7 is an enlarged view taken along line VIIVII of FIG. 3;

FIG. 8 is a view taken along line VIIIVIII of FIG. 7; and

FIG. 9 is a view taken along line IX-IX of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT The principles of the present invention are particularly useful when incorporated in a self-propelled street sweeper l0 schematically illustrated in FIG. 1. The sweeper 10 has means such as a rotatable main broom 11, a side broom 12 and a conveyor 13 for transporting materials loosened by the main broom 11 into a hopper which is disposed above a pair of drive wheels 14. The frame structure of the sweeper 10 is composed of a plurality of frame or support members for supporting the sweeping means and the hopper and includes longitudinal frame members 15 and 16 (FIG. 3) which support a single engine 17, a power splitting mechanism or device 18, a portion of a drive means generally indicated at 19 for driving the sweeping means, and a drive train generally indicated at 20 for supplying power to the drive wheels 14. While the sweeper l0 utilizes a three point suspension having dirigible wheels disposed beneath the engine 17, it should be realized that the sweeper 10 of FIG. 1 is only an illustrative example of a self-propelled sweeping device which can utilize the principles of the present invention.

As diagrammatically illustrated in FIG. 1, the engine 17 has an output shaft 21 which is connected by the power splitting mechanism or device 18 with the drive train 20 and the drive means 19. The drive train 20 includes a hydrostatic transmission 22 whose output is received by a second two speed transmission 23 which in turn is connected to a differential 24 which drives a pair of sprockets 25 of a chain drive 26 for each of the driven wheels 14.

The drive means 19 for the sweeping means such as the broom l1 and the side broom 12 includes a clutch 28 having an output shaft 29 connected by a drive shaft 30 to a gear box 31 which is connected in a driving relationship with the brooms 11 and 12 by a conventional mechanical linkage or by a conventional hydraulic linkage. The conveyor 13 is preferably driven by a separate hydraulic motor. The clutch 28 is preferably a multiple disc friction clutch controlled by a lever 33 which enables engaging and disengaging the drive means 19 to the output of the engine 17 regardless of the speed and direction of movement of the sweeper and at any engine speed.

As best illustrated in FIG. 2, the power splitting mechanism or device 18 is a gear box containing a plurality of helical gears. The output shaft 21 of the engine 17 is keyed to a gear 34 which is in driving engagement with a gear 35 keyed on a shaft such as 36 which is connected to a pump 37 of the hydrostatic transmission 22. Preferably, as illustrated in FIG. 3, the shaft 36 is connected by a flexible coupling 38 to a pump shaft 39 of the pump 37 to allow for minor misalignments between the shafts 36 and 39. The gear 34 is also in driving engagement with a gear 40 which is keyed on a shaft 41 which is an input shaft for clutch 28. By appropriately selecting the number of teeth of each of the gears 34, 35 and 40, the desired gear ratio there-between can be obtained. For example, the gear 34 has 43 teeth, the gear 35 has 45 teeth and the gear 40 has 123 teeth.

The hydrostatic transmission 22 of the drive train 20 comprises a hydraulic motor 43, which has an output shaft 44, in direct fluid communication with the pump 37 which is a variable displacement pump. As illustrated, the hydrostatic transmission 22 is what is known in the art as a back-to-back transmission. As illustrated schematically in FIG. 2, the volume and direction of displacement of the pump 37, which rotates at a constant speed which is determined by the speed of engine 17, is controlled by a control means generally indicated at 45 which control means varies the amount and direction of pivotable movement of a tilting plate or wobble plate 46 which in turn controls the stroke of the pistons 47 of the pump. As illustrated, the control device 45 has a lever 48 pivotably mounted on a housing 49 and pivotably connected to a link 50. One end of the link 50 is connected to a spool member 51 of a spool valve while the other end is mechanically connected to a shaft or rod 52, which is pivotly attached to the wobble plate 46. The plate 46 is connected by links to a pair of pistons such as 53 and 54 which are received in cylinders. The position of the piston 53 in its cylinder is determined by the fluid pressure applied thereagainst via a conduit 55. In a similar manner, the position of the piston 54 in its cylinder is determined by the fluid pressure applied thereagainst by conduit 56. The conduits 55 and 56 extend to ports of the spool valve 51 and are selectively connected to a pressure line 57 or one of a pair of drain line 58 depending on the amount and direction of the axial displacement of the spool member 51. As illustrated, movement of the lever 48 in a clockwise direction would shift the spool member 51 towards the left to vent conduit 56 and apply fluid from conduit 57 to conduit 55 to act on piston 53 to tilt or move the plate 46 in a counterclockwise direction. As the plate 46 moves towards a new position, the arm 52 changes the orientation of the lever 50 to cause the spool member 51 to move towards the right and thus stop the venting and application of fluids as the plate 46 reaches the desired angular position.

In addition to the drain lines 58 of the control means 45, the housing of the hydrostatic motor 43 is provided with an internal drain passage 61 which extends to the housing of the pump 37. From the housing of the pump 37, a second drain line 62 extends to an oil cooler 63 which is disposed in the path of an air flow created by a fan 63' which is driven by the engine 17. The oil cooler 63 discharges into a reservoir or reserve tank 64 which is provided with a commercially available reservoir breather device 65 which allows air to be bled from the reservoir at a positive pressure of psi and air to be bled into the reservoir at a negative pressure of 0.3psi. The reservoir 64 is connected by a conduit 66 which may include a filter to an intake of an oil supply or pump 67 which is positioned adjacent to the engine 17 and is driven by a belt 68. The pump 67 produces a supply of charge oil which is conducted by a conduit 68 to the housing of the transmission 22 with a portion being supplied to line 57 of the control means 45. As the charge oil enters the housing of the transmission 22, it is in communication through a check valve 69 with conduit 70 and a check valve 71 with the conduit 72. The check valves 69 and 71 are arranged to prevent escape of fluid in the conduit 70 or 72, respectively, when under a high pressure but enables addition of fluid into the respective conduits when they are acting as a return conduit between the motor 43 and pump 37. In addition, a pressure relief valve 73 connects the internal conduits for the charge oil supply to a drain such as 74 which extends to the reservoir.

The hydrostatic transmission 22 is provided with conventional means for bleeding off a portion of the fluid or oil in the close circuit extending between the pump 37 and the motor 43 for the purposes of lubricating the moving parts such as the piston 47 of the pump and the pistons 75 of the motor 43. In addition thereto, this control bled off a portion of the hydrostatic pressure, which can be accomplished by providing controlled orifices in each of the pistons 75 of the motor 43, prevents an excessive temperature rise by diverting a portion of the fluid through the cooler 63.

The hydrostatic transmission 22 discussed hereinabove, are commercially available and the above described transmission is only an example of a hydrostatic transmission that can be utilized in accordance with the present invention.

The output shaft 44 of the motor 43 is connected to the two speed transmission 23 whose output is connected through the differential 24 to the sprockets 25 for the chain drive to the drive wheels 14. The transmission 23 may be shifted from one gear ratio to a neutral position to a second or high gear ratio to provide a lower output speed for the drive wheels. While in the neutral position, free wheeling of the drive wheels will occur which enables towing of the sweeper. To control the transmission 23, a transmission shift rod is connected through a pivotable link 81 (FIG. 4) to a rod or link 82 which is adjustable and pivotably connected to a pivotable shift lever 83 extending into the operators cab or adjacent to the operators position. During most operations, the transmission 23 will be shifted to the high speed position which provides a 1:1 ratio between the output of the hydrostatic transmission 22 and the differential 24. Under certain load conditions or due to the terrain on which the sweeper is operating, such as a steep incline, it is desirable to shift to the low speed position to obtain a higher gear ratio in the drive train which provides more power for climbing hills or for going over either bumps or curbs.

As mentioned hereinabove, the position of the lever 48 for the control means 45 determines the direction and speed of rotation of the output shaft 44 of the motor 43 of the transmission 22. To shift the lever 48 to the various positions for both a reverse and forward output for the transmission, a linkage means extends to the operators position such as the operators cab and includes a manually actuated member connected by a plurality of linkage members to the lever 48. Preferably, the member 100 is a rocker type foot pedal pivotably mounted on an upstanding support 101 above the floor boards 102 of the operators compartment or cab. The pedal 100 is connected by an adjustable link 103 to a lever arm 104 which is carried on a shaft 105 which is supported for rotation beneath the floor 102. Also connected to the shaft 105 is a second lever 106 which is connected by a rod 107, whose length is adjustable, to the lever 48 of the control means 45. Thus, rocking movement of the pedal 100 on its mount 101 shifts the lever 48 to either a forward or reverse direction.

As best illustrated in FIG. 5, the lever 48 has a neutral position (in bold lines) at which the pump 37 is not producing any flor or oil output for driving the motor 43. By rotating lever 48 towards a position illustrated as 48a, the pump 37 begins pumping fluid to the motor 43 to cause the output shaft 44 to rotate in a direction causing forward movement of the sweeper 10. Movement of the lever 48 to a position illustrated at 48b causes the pump 37 to pump in a reverse direction to cause a reverse movement for the sweeper.

To limit movement of the lever 48 in the forward and reverse directions, a plate 110 having an opening 111 closed by a flange 112 is secured on the housing for the control means 45 with the lever 48 extending through the opening 111. As illustrated, an edge 113 of the opening 1 11 limits maximum movement of the lever 48 in the reverse direction which is illustrated by the position 48b. In a similar manner, maximum movement of the lever 48 in the forward direction is limited by the flange 1 12. In order to provide adjustments in the maximum forward movement, the flange 112 supports an adjustment device 114 comprising a bolt threaded therein for engaging the lever 48 as it reaches the position 48a. The plate 110 provides a safety feature which limits the maximum speed of movement of the sweeper in the reverse direction to a speed which is substantially less than the maximum forward speed.

When the lever 48 of the control means 45 is in a neutral position as illustrated in FIG. 5, the foot pedal is in a neutral position. Rotation of the foot pedal in the direction of arrow 116 (FIG. 2) rotates or pivots the control lever 48 towards the position 48a (FIG. 5) with the amount of pivoting being dependent on the amount of displacement of the pedal 100 from the neutral position. In a similar manner, rotation of the pedal 100 in a counterclockwise direction indicated by the arrow 117 from a neutral position shifts the lever 48 towards the position 48b with the amount of movement dependent on displacement of the pedal from the neutral position. In order to return the pedal 100 to a neutral position when pressure is removed therefrom, the linkage means includes biasing means which are best illustrated in FIGS. 7 and 8.

The biasing means includes a flat surface 120 which is associated with the shaft 105. As illustrated, the surface 120 is provided by a pair of members 121 which are secured to ends of shaft segments 122 and 123 and form a connection therebetween to form the shaft 105. Disposed beneath the members 121 is a plunger housing 124 which receives a plunger 125 which has a head 126 providing a flat surface 127. A spring 128 biases the plunger 125 so that the surface 127 engages the surface 120. To prevent lateral movement between the surfaces 127 and 120, the head 126 of the plunger is provided with a side flange such as a plate 129. As illustrated in broken lines in FIG. 7, rotation of the shaft 105 causes rotation of the members providing the surface 120 and the comers of the members adjacent the surface 120 force the plunger 125 against the spring 128. Upon release of pressure on the pedal 100, the spring 128 acting through the plunger 125, the members 121 will rotate the shaft 105 and thus rotate the pedal to a neutral position. The adjustable member 107 allows adjustment in its length so that when the shaft is in a neutral position, lever 48 is in a neutral position. Link 103 is adjustable to enable positioning pedal 100 in the desired orientation for the neutral position.

To facilitate assembly, the bracket 101 or pedestal for mounting the foot pedal 100 is formed of a pair of flange members which provide bearing surfaces for the shaft segment 123. As illustrated in FIG. 8, the bracket 101 extends through an aperture in the floor board and is mounted below the floor board 102 on a frame member such as 130.

To prevent starting of the engine 17 with the hydrostatic transmission in either a forward or reverse condition, the linkage means includes means for opening a starting circuit for the starting motor of the engine 17. As best illustrated in FIGS. 3 and 9, a switch which is connected in the starting circuit for the starting motor is mounted on a frame member such as 16 adjacent to the shaft 105. The switch 135 is normally open and has a spring biased plunger 136 which when depressed closes the switch elements of the switch 135. Adjacent to the switch 135 is a bracket 137 rotatably supporting the lever arm unit 138 which lever arm has a roller 139. A member 140 terminating in a curve surface is adjustably positioned by one or more clamps 141 on the shaft 105. When the foot pedal 100 is in the neutral position, the member 140 depresses the unit 138 to cause the plunger 136 to close the contacts and thus close the opening in the starting circuit. Any movement of the foot pedal 100 in the forward or reverse direction causes rotation of the shaft 105 which moves the member 140 out of engagement with the roller 139 and allows the plunger 136 to be moved to the normally open position.

In FIG. 3 the foot pedal is arranged on the right hand side of the device to provide a right hand drive. If a dual control for both right hand and left hand drive is desired, a second pedal connected by a linkage to a shaft 151, which is coupled to shaft 105, is provided. With the provision of pedal 150, a dual control of the transmission is provided. As illustrated in FIG. 3, the clutch lever 33 for the power take off unit and the clutch lever 83 for the two speed transmission are positioned in between the two control positions and easily reached by the operator from either control station.

If instead of a dual control system a single control on the left hand side of the sweeper is desired, then the pedal 150 and shaft 151 are utilized and the means for moving the pedal to a neutral position is positioned adjacent to the pedal 150 while the starter interlock or means for preventing the starting of the engine 17 is also rearranged.

As best illustrated in FIG. 7, the pedal 100 is moved by the operator who presses with his toe against a portion 100a to shift the transmission into the forward mode of operation with the amount of displacement from the neutral position determining the speed of advance. If the speed of advance is to be decreased, then applying pressure by the heel against portion 100b of the pedal 100 will rotate the pedal in the direction 117 to decrease the forward speed as the transmission approaches a neutral position and continued pressure applied to portion 10% will shift the transmission to a reverse operation.

In the street sweeper of the present invention, adjusting the speed or throttle setting for the engine 17, which is preferably provided with a governor to maintain the same rpm regardless of the load applied thereto, determines the speed for driving the sweeping means such as the main broom 11, the side broom 12 and the conveyors 13. Movement of the foot pedal 100 controls the direction and speed of movement for the sweeper without interrupting the operation of the sweeping means.

The hydrostatic transmission provides many advantages over a drive train using a friction clutch. For example, the operator can reverse direction of the sweeper 10 without shifting gears and without interrupting the sweeping means. Furthermore, the hydrostatic transmission provides dynamic braking for the sweeper. Thus, the present invention provides a sweeper which is easy to operate and which mode of operation can be changed by merely changing the pressure applied to the foot pedal 100.

The engine 17 is illustrated as an internal combustion piston engine such as either a gasoline or diesel engine. However, other types of propulsion means such as a rotary combustion engine, a turbine engine or an electric motor could be used as the single source of power for the drive train and drive means for the sweeping equip ment.

Although various minor modifications might be suggested by those versed in the art, it is to be understood that we wish to employ within the scope of the patent warranted herein all such modifications as reasonably and properly come within the scope of our contribution to the art.

We claim:

1. In a self-propelled street sweeper having sweeping means including a rotatable broom and conveyor means for depositing material dislodged by the broom into a hopper, said sweeper having a single engine with a crank shaft connected by a power splitting mechanism to a differential and sprockets of a chain drive for driving each of the driven wheels, a pair of wheels inesw r.tq pr lasllina th Sweeper a d qs l ye means for actuating the sweeping means, the improvements comprising the drive train including a hydrostatic transmission comprising a hydrostatic motor in fluid communication with a variable displacement pump which transmission includes means for controlling the volume and direction of the displacement of the pump to control the speed and direction of movement of the street sweeper, said hydrostatic transmission driving through the differential and the sprockets of the chain drive for driving each of the driven wheels, and linkage means extending from an operator position on the sweeper and connected to the control means so that the speed and direction of the movement of the street sweeper can be controlled independently of the speed of the sweeping meansfor biasingthe pedal to a neutral position and a plurality of linkage members interconnecting the pedal to the control means to transfer movement of the pedal thereto, so that movement of the pedal in one direction from the neutral position causes the hydrostatic transmission to propel the sweeper in a forward direction with the amount of movement of the pedal determining the speed of advance and movement of the pedal in the opposite direction causes the hydrostatic transmission to propel the sweeper in a reverse direction with the amount of movement of the pedal from the neutral position determining the speed of the sweeper in the reverse direction.

4. In a self-propelled street sweeper according to claim 3, wherein said linkage members include at least one shaft mounted for rotation in response to movement of said pedal, and wherein said biasing means comprises a flat surface associated with said shaft, a plunger having a flat surface, and a spring biasing the flat surface of the plunger against the flat surface associated with the shaft so that rotation of the shaft by movement of the pedal from a neutral position is resisted by said spring which rotates the shaft to return the pedal to the neutral position when pressure on the pedal is removed.

5. In a self-propelled street sweeper according to claim 4, wherein the flat surface associated with the shaft is provided on a pair of members which interconnect a pair of shaft segments together to form said shaft.

6. In a self-propelled street sweeper according to claim 3, wherein said linkage means includes a means for opening a starting circuit for said engine in response to movement of the pedal from a neutral position so that the engine can be started only with the hydrostatic transmission in a neutral position.

7. In a self-propelled street sweeper according to claim 6, wherein the means for opening a circuit includes a switch biased to an open position and having an actuating plunger to close the switch and a member in the linkage means depressing the plunger to close the switch when the pedal is in a neutral position.

8. In a self-propelled street sweeper according to claim 7, wherein at least one of the linkage members is a shaft mounted for rotation in response to movement of said pedal, and wherein said member engaging the switch is a cam member adjustably mounted on said shaft to rotate therewith.

9. In a self-propelled street sweeper according to claim 3, wherein a linkage means includes means limiting the amount of movement of the foot pedal in the opposite direction to less than the amount of movement in the one direction so that the speed of the sweeper in the reverse direction is less than the speed in the forward direction.

10. In a self-propelled street sweeper according to claim 1, wherein the drive train includes a two speed transmission interconnecting the output of the hydrostatic transmission to the pair of wheels, said two speed transmission having a neutral position and being controlled by a shift lever disposed at the operator position.

11. In a self-propelled street sweeper according to 12. A self-propelled street sweeper comprising a frame supported for movement on wheels which wheels include a pair of driven wheels, an engine mounted on said frame having an output shaft connected to a first gear, sweeping means including at least one broom mounted for rotation, means for driving the sweeping means including a second gear engaging the first gear, hydrostatic transmission comprising a hydrostatic motor having an output shaft and being in fluid communication with a variable displacement pump, said pump being driven by a third gear engaging said first gear, said transmission including means for controlling the volume and direction of displacement of the pump to control the speed and direction of rotation of the output shaft of the motor, means connected to the output shaft of the motor for transferring the output of the motor to the pair of drive wheels to move the sweeper, a manually actuated member disposed on the frame at an operator position, and linkage means interconnecting the member to the means controlling the transmission so that the direction and speed of movement of the sweeper may be controlled independent of the speed of the sweeping means.

13. A self-propelled street sweeper according to claim 12, wherein said member is a foot actuated rocker pedal mounted for pivotal movement about a neutral position and wherein said linkage means includes means biasing the pedal to said neutral position so that movement of the pedal in one direction from the neutral position causes the hydrostatic transmission to propel the sweeper in a forward direction with the amount of movement of the pedal determining the speed of advance and movement of the pedal in the opposite direction from the neutral position causes the hydrostatic transmission to propel the sweeper in a reverse direction with the amount of movement of the pedal determining the speed of the sweeper in the reverse direction.

14. A self-propelled street sweeper according to claim 13, wherein said linkage means includes at least one shaft mounted for rotation in response to movement of said pedal and a member mounted to rotate with said shaft, said member having a flat surface, and wherein said biasing means comprises a plunger having a flat surface and a spring for biasing the flat surface of the plunger against the flat surface of the member so that rotation of the shaft in response to movement of the pedal from a neutral position is resisted by the spring which rotates the shaft to return the pedal to the neutral position when the pressure on the pedal is removed.

15. A self-propelled street sweeper according to claim 13, wherein said linkage means includes a means for opening a starting circuit for said engine in response to movement of the pedal from a neutral position so that the engine can be started only with the hydrostatic transmission in a neutral position.

16. A self-propelled street sweeper according to claim 15, wherein the foot actuated rocker pedal is disposed on one side of the frame and which sweeper includes a second foot actuated rocker pedal mounted for pivotal movement on the opposite side of the frame, said second pedal being interconnected by the linkage means to the means controlling the transmission so that a sweeper has a dual control system for the hydrostatic transmission.

17. A self-propelled street sweeper according to claim 13, wherein the means for transferring includes a two speed transmission having a neutral position, said two speed transmission being controlled by a lever disposed adjacent to an operator position on the frame.

18. A self-propelled street sweeper according to claim 17, wherein the drive means for the sweeper means includes a multiple disc friction clutch which enables engaging and disengaging of the sweeping means to the second gear at any engine speed regardless of the direction and speed of movement of the sweeper.

19. A self-propelled street sweeper according to claim 18, wherein the linkage means includes means for opening a starting circuit for said engine in response to movement of the pedal from a neutral position so that the engine can be started only with a hydrostatic transmission in a neutral position. 

1. In a self-propelled street sweeper having sweeping means including a rotatable broom and conveyor means for depositing material dislodged by the broom into a hopper, said sweeper having a single engine with a crank shaft connected by a power splitting mechanism to a differential and sprockets of a chain drive for driving each of the driven wheels, a pair of wheels of the sweeper for propelling the sweeper and to drive means for actuating the sweeping means, the improvements comprising the drive train including a hydrostatic transmission comprising a hydrostatic motor in fluid communication with a variable displacement pump which transmission includes means for controlling the volume and diRection of the displacement of the pump to control the speed and direction of movement of the street sweeper, said hydrostatic transmission driving through the differential and the sprockets of the chain drive for driving each of the driven wheels, and linkage means extending from an operator position on the sweeper and connected to the control means so that the speed and direction of the movement of the street sweeper can be controlled independently of the speed of the sweeping means.
 2. In a self-propelled street sweeper according to claim 1, wherein the drive means for the sweeping means includes a multiple disc friction clutch which enables engaging and disengaging the sweeping means to the power splitting mechanism at any engine speed and regardless of the direction and speed of the movement of the sweeper.
 3. In a self-propelled street sweeper according to claim 1, wherein said linkage means includes a foot actuated rocker pedal mounted for pivotable movement, means for biasing the pedal to a neutral position and a plurality of linkage members interconnecting the pedal to the control means to transfer movement of the pedal thereto, so that movement of the pedal in one direction from the neutral position causes the hydrostatic transmission to propel the sweeper in a forward direction with the amount of movement of the pedal determining the speed of advance and movement of the pedal in the opposite direction causes the hydrostatic transmission to propel the sweeper in a reverse direction with the amount of movement of the pedal from the neutral position determining the speed of the sweeper in the reverse direction.
 4. In a self-propelled street sweeper according to claim 3, wherein said linkage members include at least one shaft mounted for rotation in response to movement of said pedal, and wherein said biasing means comprises a flat surface associated with said shaft, a plunger having a flat surface, and a spring biasing the flat surface of the plunger against the flat surface associated with the shaft so that rotation of the shaft by movement of the pedal from a neutral position is resisted by said spring which rotates the shaft to return the pedal to the neutral position when pressure on the pedal is removed.
 5. In a self-propelled street sweeper according to claim 4, wherein the flat surface associated with the shaft is provided on a pair of members which interconnect a pair of shaft segments together to form said shaft.
 6. In a self-propelled street sweeper according to claim 3, wherein said linkage means includes a means for opening a starting circuit for said engine in response to movement of the pedal from a neutral position so that the engine can be started only with the hydrostatic transmission in a neutral position.
 7. In a self-propelled street sweeper according to claim 6, wherein the means for opening a circuit includes a switch biased to an open position and having an actuating plunger to close the switch and a member in the linkage means depressing the plunger to close the switch when the pedal is in a neutral position.
 8. In a self-propelled street sweeper according to claim 7, wherein at least one of the linkage members is a shaft mounted for rotation in response to movement of said pedal, and wherein said member engaging the switch is a cam member adjustably mounted on said shaft to rotate therewith.
 9. In a self-propelled street sweeper according to claim 3, wherein a linkage means includes means limiting the amount of movement of the foot pedal in the opposite direction to less than the amount of movement in the one direction so that the speed of the sweeper in the reverse direction is less than the speed in the forward direction.
 10. In a self-propelled street sweeper according to claim 1, wherein the drive train includes a two speed transmission interconnecting the output of the hydrostatic transmission to the pair of wheels, said two speed transmission having a neutral position and being controlled by a shift lever dispOsed at the operator position.
 11. In a self-propelled street sweeper according to claim 1, which further includes an oil reservoir connected to an oil supply pump driven by said engine having an output under pressure connected to the hydrostatic transmission, means connected to the hydrostatic transmission for removing a portion of the fluid therefrom and conveying it to a cooler, said cooler discharging into said reservoir.
 12. A self-propelled street sweeper comprising a frame supported for movement on wheels which wheels include a pair of driven wheels, an engine mounted on said frame having an output shaft connected to a first gear, sweeping means including at least one broom mounted for rotation, means for driving the sweeping means including a second gear engaging the first gear, hydrostatic transmission comprising a hydrostatic motor having an output shaft and being in fluid communication with a variable displacement pump, said pump being driven by a third gear engaging said first gear, said transmission including means for controlling the volume and direction of displacement of the pump to control the speed and direction of rotation of the output shaft of the motor, means connected to the output shaft of the motor for transferring the output of the motor to the pair of drive wheels to move the sweeper, a manually actuated member disposed on the frame at an operator position, and linkage means interconnecting the member to the means controlling the transmission so that the direction and speed of movement of the sweeper may be controlled independent of the speed of the sweeping means.
 13. A self-propelled street sweeper according to claim 12, wherein said member is a foot actuated rocker pedal mounted for pivotal movement about a neutral position and wherein said linkage means includes means biasing the pedal to said neutral position so that movement of the pedal in one direction from the neutral position causes the hydrostatic transmission to propel the sweeper in a forward direction with the amount of movement of the pedal determining the speed of advance and movement of the pedal in the opposite direction from the neutral position causes the hydrostatic transmission to propel the sweeper in a reverse direction with the amount of movement of the pedal determining the speed of the sweeper in the reverse direction.
 14. A self-propelled street sweeper according to claim 13, wherein said linkage means includes at least one shaft mounted for rotation in response to movement of said pedal and a member mounted to rotate with said shaft, said member having a flat surface, and wherein said biasing means comprises a plunger having a flat surface and a spring for biasing the flat surface of the plunger against the flat surface of the member so that rotation of the shaft in response to movement of the pedal from a neutral position is resisted by the spring which rotates the shaft to return the pedal to the neutral position when the pressure on the pedal is removed.
 15. A self-propelled street sweeper according to claim 13, wherein said linkage means includes a means for opening a starting circuit for said engine in response to movement of the pedal from a neutral position so that the engine can be started only with the hydrostatic transmission in a neutral position.
 16. A self-propelled street sweeper according to claim 15, wherein the foot actuated rocker pedal is disposed on one side of the frame and which sweeper includes a second foot actuated rocker pedal mounted for pivotal movement on the opposite side of the frame, said second pedal being interconnected by the linkage means to the means controlling the transmission so that a sweeper has a dual control system for the hydrostatic transmission.
 17. A self-propelled street sweeper according to claim 13, wherein the means for transferring includes a two speed transmission having a neutral position, said two speed transmission being controlled by a lever disposed adjacent to an operator position on the frame.
 18. A self-propelled street sweeper according to claim 17, wherein the drive means for the sweeper means includes a multiple disc friction clutch which enables engaging and disengaging of the sweeping means to the second gear at any engine speed regardless of the direction and speed of movement of the sweeper.
 19. A self-propelled street sweeper according to claim 18, wherein the linkage means includes means for opening a starting circuit for said engine in response to movement of the pedal from a neutral position so that the engine can be started only with a hydrostatic transmission in a neutral position. 